The evolution of human language, and the kind of thought the communication of which requires it, raises considerable explanatory challenges. These systems of representation constitute a radical discontinuity in the natural world. Even species closely related to our own appear incapable of either thought or talk with the recursive structure, generalized systematicity, and task-domain neutrality that characterize human talk and the thought it expresses. W. Tecumseh Fitch’s proposal (2004, in press) that human language is descended from a sexually selected, prosodic (...) proto-language that approximated its syntactic complexity, and later acquired semantics thanks to kin selection for its use as a means of pedagogical transmission, has the promise of meeting these explanatory challenges. However, Fitch’s theory raises two problems of its own: (1) according to Boyd and Richerson (1996, Proc. Br. Acad. 88: 77–93), circumstances in which pedagogy is adaptive are inevitably rare in nature, and (2) it is unlikely that our non-discursive precursors had generally systematic, task-domain neutral thoughts to communicate to their offspring. I propose solutions to these problems. Pedagogy would be favored in a population where complex rituals dominated diverse aspects of life. Prosodic proto-language could emerge as the medium of pedagogic transmission. As this medium was used to teach a greater variety of tasks, it would become increasingly general and domain neutral. The presence and importance of such a system of communication in hominid populations could then drive, via Baldwinian mechanisms, the evolution of a kind of ‘thinking for speaking’ (Slobin 1991, Pragmatics 1: 7–25) characterized by recursive structure, generalized systematicity, and task-domain neutrality. (shrink)

The present discussion of sociobiological approaches to ethnic nepotism takes Pierre van den Berghe ʼs theory as a starting point. Two points, which have not been addressed in former analyses, are considered to be of particular importance. It is argued that the behavioral mechanism of ethnic nepotism—as understood by van den Berghe—cannot explain ethnic boundaries and attitudes. In addition, I show that van den Bergheʼs central premise concerning ethnic nepotism is in contradiction to Hamiltonʼs formula, the essential principle of kin (...)selection theory. It is further discussed how other approaches that make reference to ethnic nepotism are related to van den Bergheʼs account and its problems. I conclude with remarks on the evolutionary explanation of ethnic phenomena. (shrink)

My comments will focus on the second and third chapters of Sober’s book , which explore Darwin’s ideas about altruism, group selection and kin selection , and sex-ratio evolution . Sober makes a persuasive argument for his main claim: that Darwin was a subtler thinker on these topics than he is often taken to be. While there is much that I admire in Sober’s lucid discussion, I will focus on points of disagreement. Readers should note that this is (...) not the first time that Sober and I have disagreed on these issues .Sober begins his chapter on group selection with a brief history of the modern debate on the topic, which began in earnest in the 1960s. One of the key figures in this debate was George Williams, whose book Adaptation and Natural Selection helped convince many biologists that group selection was unlikely to be an important factor in evolution. Sober is critical of many of Williams’ arguments, though .. (shrink)

We demonstrate the existence of altruism via kin selection in artificial life and explore its nuances. We do so in the Avida system through a setup that is based on the behavior of colicinogenic bacteria: Organisms can kill unrelated organisms in a given radius but must kill themselves to do so. Initially, we confirm!results found in the bacterial world: Digital organisms do sacrifice themselves for their kin—an extreme example of altruism— and do so more often in structured environments, where (...) kin are always nearby, than in well-mixed environments, where the location of kin is stochastically determined. Having shown that helping one’s kin is advantageous, we turn our attention to investigating the efficacy and implications of the strategies of kincheaters, those who receive help from kin but do not return it. Contrary to the expectations of current theory, we find that kin-cheaters outcompete kin-altruists. Our results cause us to question the stability of strategies that involve altruism between kin. Knowing that kin-altruism persists in biological systems, however, we search for, and find, conditions that allow!kin-based altruism to persist in evolving!systems despite the!presence of kin-cheaters. (shrink)

In the analysis of intergenerational transfer, several improvements can be made. First, following kin selection theory, grandparents have kin other than grandchildren in which to invest and therefore any investigation into grandparents should take this perspective. Secondly, how transfers actually enhance the survivorship of younger relatives such as grandchildren must be better measured, especially in the ethnographic literature. Finally, the problem of indirect investments or targeting must be considered.

The levels of selection problem was central to Maynard Smith’s work throughout his career. This paper traces Maynard Smith’s views on the levels of selection, from his objections to group selection in the 1960s to his concern with the major evolutionary transitions in the 1990s. The relations between Maynard Smith’s position and those of Hamilton and G.C. Williams are explored, as is Maynard Smith’s dislike of the Price equation approach to multi-level selection. Maynard Smith’s account of (...) the ‘core Darwinian principles’ is discussed, as is his debate with Sober and Wilson (1998) over the status of trait-group models, and his attitude to the currently fashionable concept of pluralism about the levels of selection. (shrink)

This paper presents a comparison of social kinship (patrilineage) and biological kinship (genetic relatedness) in predicting cooperative relationships in two different economic contexts in the fishing and whaling village of Lamalera, Indonesia. A previous analysis (Alvard, Human Nature 14:129–163, 2003) of boat crew affiliation data collected in the village in 1999 found that social kinship (patrilineage) was a better predictor of crew affiliation than was genetic kinship. A replication of this analysis using similar data collected in 2006 finds the same (...) pattern: lineage is a better predictor than genetic kinship of crew affiliation, and the two together explain little additional variance over that explained by lineage alone. However, an analogous test on food-sharing relationships finds the opposite pattern: biological kinship is a better predictor of food-sharing relationships than is social kinship. The difference between these two cooperative contexts is interpreted in terms of kin preferences that shape partner choice, and the relative autonomy with which individuals can seek to satisfy those preferences. Drawing on stable matching theory, it is suggested that unilineal descent may serve as a stable compromise among multiple individuals’ incongruent partner preferences, with patriliny favored over matriliny in the crew-formation context because it leads to higher mean degrees of relatedness among male cooperators. In the context of food-sharing, kin preferences can be pursued relatively autonomously, without the necessity of coordinating preferences with those of other households through the institution of lineage. (shrink)

I argue that evolutionary strategies of kin selection and game-theoretic reciprocity are apt to generate agent-centered and agent- neutral moral intuitions, respectively. Such intuitions are the building blocks of moral theories, resulting in a fundamental schism between agent-centered theories on the one hand and agent-neutral theories on the other. An agent-neutral moral theory is one according to which everyone has the same duties and moral aims, no matter what their personal interests or interpersonal relationships. Agent-centered moral theories deny this (...) and include at least some prescriptions that include ineliminable indexicals. I argue that there are no rational means of bridging the gap between the two types of theories; nevertheless this does not necessitate skepticism about the moral—we might instead opt for an ethical relativism in which the truth of moral statements is relativized to the perspective of moral theories on either side of the schism. Such a relativism does not mean that any ethical theory is as good as any other; some cannot be held in reflective equilibrium, and even among those that can, there may well be pragmatic reasons that motivate the selection of one theory over another. But if no sort of relativism is deemed acceptable, then it is hard to avoid moral skepticism. (shrink)

A simple and general criterion is derived for the evolution of altruism when individuals interact in pairs. It is argued that the treatment of this problem in kin selection theory and in game theory are special cases of this general criterion.

In an incendiary 2010 Nature article, M. A. Nowak, C. E. Tarnita, and E. O. Wilson present a savage critique of the best-known and most widely used framework for the study of social evolution, W. D. Hamilton’s theory of kin selection. More than a hundred biologists have since rallied to the theory’s defence, but Nowak et al. maintain that their arguments ‘stand unrefuted’. Here I consider the most contentious claim Nowak et al. defend: that Hamilton’s rule, the core explanatory (...) principle of kin selection theory, ‘almost never holds’. I first distinguish two versions of Hamilton’s rule in contemporary theory: a special version (HRS) that requires restrictive assumptions, and a general version (HRG) that does not. I then show that Nowak et al. are most charitably construed as arguing that HRS almost never holds, while HRG buys its generality at the expense of explanatory power. While their arguments against HRS are fairly uncontroversial, their arguments against HRG are more contentious, yet these have been largely overlooked in the ensuing furore. I consider the arguments for and against the explanatory value of HRG, with a view to assessing what exactly is at stake in the debate. I suggest that the debate hinges on issues concerning the causal interpretability of regression coefficients, and concerning the explanatory function Hamilton’s rule is intended to serve. (shrink)

Edward O. Wilson’s recent decision to abandon kin selection theory has sent shockwaves throughout the biological sciences. Over the past two years, more than a hundred biologists have signed letters protesting his reversal. Making sense of Wilson’s decision and the controversy it has spawned requires familiarity with the historical record. This entails not only examining the conditions under which kin selection theory first emerged, but also the organicist tradition against which it rebelled. In similar fashion, one must not (...) only examine Wilson’s long career, but also those thinkers who influenced him most, especially his intellectual grandfather, William Morton Wheeler (1865–1937). Wilson belongs to a long line of organicists, biologists whose research highlighted integration and coordination, many of whom struggled over the exact same biological riddles that have long defined Wilson’s career. Drawing inspiration (and sometimes ideas) from these intellectual forebears, Wilson is confident that he has finally identified the origin of the social impulse. (shrink)

Recent analyses of food sharing in small-scale societies indicate that reciprocal altruism maintains interhousehold food transfers, even among close kin. In this study, matrix-based regression methods are used to test the explanatory power of reciprocal altruism, kin selection, and tolerated scrounging. In a network of 35 households in Nicaragua’s Bosawas Reserve, the significant predictors of food sharing include kinship, interhousehold distance, and reciprocity. In particular, resources tend to flow from households with relatively more meat to closely related households with (...) little, as predicted by kin selection. This generalization is especially true of household dyads with mother-offspring relationships, which suggests that studies of food sharing may benefit from distinctions between lineal and collateral kin. Overall, this analysis suggests that exchanges among kin are primarily associated with differences in need, not reciprocity. Finally, although large game is distributed widely, qualitative observations indicate that hunters typically do not relinquish control of the distribution in ways predicted by costly signaling theory. (shrink)

Chagnon’s analysis of a well-known axe fight in the Yanomamö village of Mishimishiböwei-teri (Chagnon and Bugos 1979) is among the earliest empirical tests of kin selection theory for explaining cooperation in humans. Kin selection theory describes how cooperation can be organized around genetic kinship and is a fundamental tool for understanding cooperation within family groups. Previous analysis on groups of cooperative Lamaleran whale hunters suggests that the role of genetic kinship as a principle for organizing cooperative human groups (...) could be less important in certain cases than previously thought (Alvard Human Nature 14:129–163, 2003b). Evidence that supports a strong role for genetic kinship—groups are found to be more related than expected by chance—may be spurious because of the correlation between social structure and genetic kinship. Reanalysis of Chagnon’s data using matrix regression techniques, however, confirms that genetic kinship was the primary organizing principle in the axe fight; affinal relations were also important, whereas lineage identity explained nothing. (shrink)

Cooperative child care among humans, where individuals other than the biological mother (allomothers) provide care, may increase a mother’s fertility and the survivorship of her children. Although the potential benefits to the mother are clear, the motivations for allomothers to provide care are less clear. Here, we evaluate the kin selection allomothering hypothesis using observations on Hadza hunter-gatherers collected in ten camps over 17 months. Our results indicate that related allomothers spend the largest percentage of time holding children. The (...) higher the degree of relatedness among kin, the more time they spend holding, supporting the hypothesis of nepotism as the strongest motivation for providing allomaternal care. Unrelated helpers of all ages also provide a substantial amount of investment, which may be motivated by learning to mother, reciprocity, or coercion. (shrink)

Reproductive senescence in human females takes place long before other body functions senesce. This fact presents an evolutionary dilemma since continued reproduction should generally be favored by natural selection. Two commonly proposed hypotheses to account for human menopause are (a) a recent increase in the human lifespan and (b) a switch to investment in close kin rather than direct reproduction. No support is found for the proposition that human lifespans have only recently increased. Data from Ache hunter-gatherers are used (...) to test the kin selection hypothesis. Ache data do not support the proposition that females can gain greater fitness benefits in old age by helping kin rather than continuing to reproduce. Nevertheless, one crucial parameter in the model, when adjusted to the highest value within the measured 95% confidence interval, would lead to the evolution of reproductive senescence at about 53 years of age. Further investigation is necessary to determine whether the kin selection hypothesis of menopause can account for its current maintenance in most populations. (shrink)

The kin selection hypothesis posits that male androphilia (male sexual attraction to adult males) evolved because androphilic males invest more in kin, thereby enhancing inclusive fitness. Increased kin-directed altruism has been repeatedly documented among a population of transgendered androphilic males, but never among androphilic males in other cultures who adopt gender identities as men. Thus, the kin selection hypothesis may be viable if male androphilia was expressed in the transgendered form in the ancestral past. Using the Standard Cross-Cultural (...) Sample (SCCS), we examined 46 societies in which male androphilia was expressed in the transgendered form (transgendered societies) and 146 comparison societies (non-transgendered societies). We analyzed SCCS variables pertaining to ancestral sociocultural conditions, access to kin, and societal reactions to homosexuality. Our results show that ancestral sociocultural conditions and bilateral and double descent systems were more common in transgendered than in non-transgendered societies. Across the entire sample, descent systems and residence patterns that would presumably facilitate increased access to kin were associated with the presence of ancestral sociocultural conditions. Among transgendered societies, negative societal attitudes toward homosexuality were unlikely. We conclude that the ancestral human sociocultural environment was likely conducive to the expression of the transgendered form of male androphilia. Descent systems, residence patterns, and societal reactions to homosexuality likely facilitated investments in kin by transgendered males. Given that contemporary transgendered male androphiles appear to exhibit elevated kin-directed altruism, these findings further indicate the viability of the kin selection hypothesis. (shrink)

The human ability to form large, coordinated groups is among our most impressive social adaptations. Larger groups facilitate synergistic economies of scale for cooperative breeding, such economic tasks as group hunting, and success in conflict with other groups. In many organisms, genetic relationships provide the structure for sociality to evolve via the process of kin selection, and this is the case, to a certain extent, for humans. But assortment by genetic affiliation is not the only mechanism that can bring (...) people together. Affinity based on symbolically mediated and socially constructed identity, or cultural kinship, structures much of human ultrasociality. This paper examines how genetic kinship and two kinds of cultural kinship—affinal kinship and descent—structure the network of cooperating whale hunters in the village of Lamalera, Indonesia. Social network analyses show that each mechanism of assortment produces characteristic networks of different sizes, each more or less conducive to the task of hunting whales. Assortment via close genetic kin relationships (r = 0.5) produces a smaller, denser network. Assortment via less-close kin relations (r = 0.125) produces a larger but less dense network. Affinal networks are small and diffuse; lineage networks are larger, discrete, and very dense. The roles that genetic and cultural kinship play for structuring human sociality is discussed in the context of these results. (shrink)

This paper addresses methodological and metatheoretical aspects of the ongoing debate over the adaptive significance of Tibetan polyandry. Methodological contributions include a means of estimating relatedness of fraternal co-husbands given multigenerational polyandry, and use of Hamilton’s rule and a member-joiner model to specify how inclusive fitness gains of co-husbands may vary according to seniority, opportunity costs, and group size. These methods are applied to various data sets, particularly that of Crook and Crook (1988). The metatheoretical discussion pivots on the critique (...) by evolutionary psychologists of adaptationist accounts of polyandry. Contrary to this critique, I argue that valid adaptationist explanations of such practices do not necessitate cognitive mechanisms evolved specifically to produce polyandry, nor that there must have been exact equivalents of Tibetan agricultural estates and social institutions in human evolutionary history. Specific issues raised when one posits either kin selection or cultural evolution to explain the adaptive features of Tibetan polyandry are also discussed. (shrink)

Abstract. Scientists have long puzzled over how homosexual orientation has evolved, given the assumed low relative fitness of homosexual individuals compared to heterosexual individuals. A number of theoretical models for the evolution of homosexuality have been postulated including balance polymorphism, "Fertile females", hypervariability of DNA sequences, kin selection, and "parental manipulation". In this paper, I propose a new group-selection model for the evolution of homosexuality which offers two advantages over existing models: (1) its non-assumption of genetic determinism, and (...) (2) its lack of dependency on an inefficient altruism relation and family dynamics theory. (shrink)

For many years the evolution of language has been seen as a disreputable topic, mired in fanciful “just so stories” about language origins. However, in the last decade a new synthesis of modern linguistics, cognitive neuroscience and neo-Darwinian evolutionary theory has begun to make important contributions to our understanding of the biology and evolution of language. I review some of this recent progress, focusing on the value of the comparative method, which uses data from animal species to draw inferences about (...) language evolution. Discussing speech first, I show how data concerning a wide variety of species, from monkeys to birds, can increase our understanding of the anatomical and neural mechanisms underlying human spoken language, and how bird and whale song provide insights into the ultimate evolutionary function of language. I discuss the “descended larynx” of humans, a peculiar adaptation for speech that has received much attention in the past, which despite earlier claims is not uniquely human. Then I will turn to the neural mechanisms underlying spoken language, pointing out the difficulties animals apparently experience in perceiving hierarchical structure in sounds, and stressing the importance of vocal imitation in the evolution of a spoken language. Turning to ultimate function, I suggest that communication among kin (especially between parents and offspring) played a crucial but neglected role in driving language evolution. Finally, I briefly discuss phylogeny, discussing hypotheses that offer plausible routes to human language from a non-linguistic chimp-like ancestor. I conclude that comparative data from living animals will be key to developing a richer, more interdisciplinary understanding of our most distinctively human trait: language. (shrink)

Two questions are raised for Grafen’s formal darwinism project of aligning evolutionary dynamics under natural selection with the optimization of phenotypes for individuals of a population. The first question concerns mean fitness maximization during frequency-dependent selection; in such selection regimes, not only is mean fitness typically not maximized but it is implausible that any parameter closely related to fitness is being maximized. The second question concerns whether natural selection on inclusive fitness differences can be regarded as (...) individual selection or whether it leads to a departure from the central motivation that led to the formal darwinism project, viz., to show that “Darwinian” evolution through individual selection leads to “good design” or phenotypic adaptation through trait optimization. (shrink)

Birth order has been examined over a wide variety of dimensions in the context of modern populations. A consistent message has been that it is better to be born first. The analysis of birth order in this paper is different in several ways from other investigations into birth order effects. First, we examine the effect of birth order in an egalitarian, small-scale, kin-based society, which has not been done before. Second, we use a different outcome measure, fertility, rather than outcome (...) measures of social, psychological, or economic success. We find, third, that being born late in an egalitarian, technologically simple society rather than being born early has a positive outcome on fertility, and fourth, that number of older siblings and sibling set size are even stronger predictors of fertility, especially for males. (shrink)

Sex differences in behavior are most interesting when they are the result of inherent differences in the operational rules motivating behavior and not merely a reflection of differing life history experiences. American men and women exhibit a few differences in testamentary patterns of property allocation that appear to be due to inherently different rules of allocation. Even when analyses control for resources and surviving kin configurations, women distribute their property among a greater number of individual beneficiaries than do men. The (...) most striking differences in property allocation between men and women occur within the nuclear family and reflect differences in reproductive life span and the resulting reproductive conflicts between spouses that can endure beyond death. (shrink)

Inclusive fitness theory provides a compelling explanation for the evolution of altruism among kin. However, a completely satisfactory account of non-kin altruism is still lacking. The present study compared the level of altruism found among siblings with that found among friends and mates and sought to reconcile the findings with an evolutionary explanation for human altruism. Participants (163 males and 156 females) completed a questionnaire about help given to a sibling, friend, or mate. Overall, participants gave friends and mates as (...) much or more help than they gave siblings. However, as the cost of help increased, siblings received a progressively larger share of the help, whereas friends and mates received a progressively smaller share, despite the fact that participants were closer emotionally to friends and mates than they were to siblings. These findings help to explain the relative standing of friends and mates as recipients of altruistic aid. (shrink)

Low birth rates in developed societies reflect women’s difficulties in combining work and motherhood. While demographic research has focused on the role of formal childcare in easing this dilemma, evolutionary theory points to the importance of kin. The cooperative breeding hypothesis states that the wider kin group has facilitated women’s reproduction during our evolutionary history. This mechanism has been demonstrated in pre-industrial societies, but there is no direct evidence of beneficial effects of kin’s support on parents’ reproduction in modern societies. (...) Using three-generation longitudinal data anchored in a sample of grandparents aged 55 and over in 1992 in the Netherlands, we show that childcare support from grandparents increases the probability that parents have additional children in the next 8 to 10 years. Grandparental childcare provided to a nephew or niece of childless children did not significantly increase the probability that those children started a family. These results suggest that childcare support by grandparents can enhance their children’s reproductive success in modern societies and is an important factor in people’s fertility decisions, along with the availability of formal childcare. (shrink)

Exploitation is a fundamental element of the parental strategies of many species of birds. Cuckoos, for example, lay their eggs in the nest of other birds, who often unwittingly rear the alien nestlings as their own. Nest parasitism is an efficient reproductive strategy for cuckoos, who do not have to worry about building a nest, incubating their eggs, or feeding their nestlings. But not all hosts respond passively to such intrusions. In response to parasitic cowbirds, for example, robins have evolved (...) the ability to detect and selectively eject alien young from their nests. Human parenting strategies differ sharply from the strategies of cuckoos and robins. Unlike cuckoos, we are reluctant to allow our children to be raised by others. Unlike robins, we knowingly rear strange young. What makes human behavior toward children so different from that of cuckoos and robins? Humans seem to share a number of predispositions that facilitate successful adoptive relationships, and the desire to raise children seems to be pervasive among modern humans. Despite these commonalities, patterns of adoption transactions vary greatly among contemporary human societies. This paper considers the origins and causes of cross-cultural variation in human adoptive behavior from an evolutionary perspective. (shrink)

Altruism is a malleable notion that is understood differently in various disciplines. The common denominator of most definitions of altruism is the idea of unidirectional helping behaviour. However, a closer examination reveals that the term altruism sometimes refers to the outcomes of a helping behaviour for the agent and its neighbours – i.e. reproductive altruism – and sometimes to what motivates the agent to help others – i.e. psychological altruism. Since these perspectives on altruism are crucially different, it is important (...) to use a clear terminology to avoid confusion. In particular, we show that the notion of altruism used by biologists profoundly differs from the ones used by philosophers, psychologists and economists in cross-disciplinary debates about human altruism. (shrink)

Cooperation is rife in the microbial world, yet our best current theories of the evolution of cooperation were developed with multicellular animals in mind. Hamilton’s theory of inclusive fitness is an important case in point: applying the theory in a microbial setting is far from straightforward, as social evolution in microbes has a number of distinctive features that the theory was never intended to capture. In this article, I focus on the conceptual challenges posed by the project of extending Hamilton’s (...) theory to accommodate the effects of gene mobility. I begin by outlining the basics of the theory of inclusive fitness, emphasizing the role that the concept of relatedness is intended to play. I then provide a brief history of this concept, showing how, over the past fifty years, it has departed from the intuitive notion of genealogical kinship to encompass a range of generalized measures of genetic similarity. I proceed to argue that gene mobility forces a further revision of the concept. The reason in short is that, when the genes implicated in producing social behaviour are mobile, we cannot talk of an organism’s genotype simpliciter; we can talk only of an organism’s genotype at a particular stage in its life cycle. We must therefore ask: with respect to which stage(s) in the life cycle should relatedness be evaluated? For instance: is it genetic similarity at the time of social interaction that matters to the evolution of social behaviour, or is it genetic similarity at the time of reproduction? I argue that, strictly speaking, it is neither of these: what really matters to the evolution of social behaviour is diachronic genetic similarity between the producers of fitness benefits at the time they produce them and the recipients of those benefits at the end of their life-cycle. I close by discussing the implications of this result. The main payoff is that it makes room for a possible new mechanism for the evolution of altruism in microbes that does not require correlated interaction among bearers of the genes for altruism. The importance of this mechanism in nature remains an open empirical question. (shrink)

Here, in textbook style, is a concise biological account of the evolution of morality. It addresses morality on three levels: moral outcomes (behavioral genetics), moral motivation or intent (psychology and neurology), and moral systems (sociality). The rationale for teaching this material is addressed in Allchin (2009). Classroom resources (including accompanying images and video links) and a discussion of teaching strategies are provided online at: http://EvolutionOfMorality.net.

We live in interesting times. Two well-known biologists — E. O. Wilson and Richard Dawkins — and some of their well-known colleagues, who used to employ broadly similar selection models, now deeply disagree over the role of group selection in the evolution of eusociality (or so we argue). Yet they describe their models as interchangeable. As philosophers of biology, we wonder whether there is substantial (i.e., empirical) disagreement here at all, and, if there is, what is this disagreement (...) about? We argue that a substantial disagreement over the processes that caused eusociality best explains this debate, yet the common practice of using overarching definitions for “group selection” and “kin selection” renders empirical differences difficult to detect. We suggest Michael J. Wade’s use of these terms as a basis for models that reveal different selection processes. Wade’s models predict different outcomes for different processes and thus can be tested. (shrink)

On the basis of distinctions between those properties of entities that can be defined without reference to other entities and those that (in different ways) cannot, this note argues that non-trivial forms of frequency-dependent selection of entities should be interpreted as selection occurring at a level higher than that of those entities. It points out that, except in degenerately simple cases, evolutionary game-theoretic models of selection are not models of individual selection. Similarly, models of genotypic (...) class='Hi'>selection such as heterosis cannot be legitimately interpreted as models of genic selection. The analysis presented here supports the views that: (i) selection should be viewed as a multi-level process; (ii) upper-level selection is ubiquitous; (iii) kin selection should be viewed as a type of group selection rather than individual selection; and (iv) inclusive fitness is not an individual property. (shrink)

The phenomenon of altruism extends from the biological realm to the human sociocultural realm. This article sketches a coherent outline of multiple types of altruism of progressively increasing scope that span these two realms and are grounded in an ever-expanding sense of “self.” Discussion of this framework notes difficulties associated with altruism at different levels. It links scientific ideas about the evolution of cooperation and about hierarchical order to perennial philosophical and religious concerns. It offers a conceptual background for inquiry (...) into societal challenges that call for altruistic behavior, especially the challenge of environmental and social sustainability. (shrink)

Four models commonly employed in sharing analyses (reciprocal altruism [RA], tolerated scrounging [TS], costly signaling [CS], and kin selection [KS]) have common features which render rigorous testing of unique predictions difficult. Relaxed versions of these models are discussed in an attempt to understand how the underlying principles of delayed returns, avoiding costs, building reputation, and aiding biological kin interact in systems of sharing. Special attention is given to the interpretation of contingency measures that critically define some form of reciprocal (...) altruism. (shrink)

By analyzing legacies in California from 1890 to 1984 Judge and Hrdy (1992) detected a gender-related difference: Men with children were statistically more likely to leave all of their property to a wife than were mothers to a husband. The authors argue that men were more likely than women to remarry and have additional children. Thus, in order to transfer their wealth to their mutual children, men can leave it to their wives but women can avoid risks by giving it (...) to the children directly. This hypothesis was tested by two experiments in which subjects were asked to put themselves in the position of a person writing a will and allocate the wealth to the surviving spouse and the children. Age and sex of the heir/heiress were experimentally varied. The results support the inclusive fitness interpretation. (shrink)

This study examines the socioeconomic and familial background of Irish Catholic priests born between 1867 and 1911. Previous research has hypothesized that lack of marriage opportunities may influence adoption of celibacy as part of a religious institution. The present study traced data from Irish seminary registries for 46 Catholic priests born in County Limerick, Ireland, using 1901 Irish Census returns and Land Valuation records. Priests were more likely to originate from landholding backgrounds, and with landholdings greater in size and wealth (...) than the local average. Priests were found to originate from families with more sons than the national average, but with similar numbers of daughters. These findings are discussed in relation to competition for resources and lineage survival strategies. (shrink)

Androphilia refers to sexual attraction and arousal to adult males, whereas gynephilia refers to sexual attraction and arousal to adult females. In Independent Samoa, androphilic males, most of whom are effeminate or transgendered, are referred to as fa’afafine, which means “in the manner of a woman.” Previous research has established that fa’afafine report significantly higher avuncular tendencies relative to gynephilic men. We hypothesized that Samoan fa’afafine might adopt feminine gender role orientations with respect to childcare activity. If so, then the (...) fa’afafine’s femininity might be a proximate mechanism for promoting their elevated avuncular tendencies. Our analyses indicated that fa’afafine had significantly higher willingness to assist in the childcare of nieces and nephews than childless women, mothers, or men, none of whom differed from each other on this measure. Thus, femininity does not appear to explain the fa’afafine’s pattern of avuncular tendencies, nor the women’s pattern of materteral (i.e., aunt-like) tendencies, relative to gynephilic men. We discuss how the fa’afafine “third” gender status might influence the expression of their elevated avuncular tendencies. (shrink)

Exponential random graph modeling (ERGM) is used here to test hypotheses derived from human behavioral ecology about the adaptive nature of human food sharing. Respondents in all (n = 317) households in the fishing and sea-hunting village of Lamalera, Indonesia, were asked to name those households to whom they had more frequently given (and from whom they had more frequently received) food during the preceding sea-hunting season. The responses were used to construct a social network of between-household food-sharing relationships in (...) the village. The results show that kinship, proximity, and reciprocal sharing all strongly increase the probability of giving food to a household. The effects of kinship and distance are relatively independent of each other, although reciprocity is more common among residentially and genealogically close households. The results show support for reciprocal altruism as a motivation for food sharing, while kinship and distance appear to be important partner-choice criteria. (shrink)

The ‘levels of selection’ question is one of the most fundamental in evolutionary biology, for it arises directly from the logic of Darwinism. As is well-known, the principle of natural selection is entirely abstract; it says that any entities satisfying certain conditions will evolve by natural selection, whatever those entities are. (These conditions are: variability, associated fitness differences, and heritability (cf. Lewontin 1970).) This fact, when combined with the fact that the biological world is hierarchically structured, i.e. (...) smaller biological units are nested within larger ones, gives rise to the levels of selection question. For in principle, entities at many different hierarchical levels, above and below that of the ‘individual organism’, (e.g. gene, chromosome, cell, kin group, colony, lineage, species) can satisfy the requirements for Darwinian evolution. This possibility has long been recognised by biologists, from Darwin himself to contemporary proponents of ‘multi-level selection’; and there exist numerous biological phenomena which suggest that it has actually occurred. (shrink)

Kin selection, reciprocity and group selection are widely regarded as evolutionary mechanisms capable of sustaining altruism among humans andother cooperative species. Our research indicates, however, that these mechanisms are only particular examples of a broader set of evolutionary possibilities.In this paper we present the results of a series of simple replicator simulations, run on variations of the 2–player prisoner's dilemma, designed to illustrate the wide range of scenarios under which altruism proves to be robust under evolutionary pressures. The (...) set of mechanisms we explore is divided into four categories:correlation, group selection, imitation, and punishment. We argue that correlation is the core phenomenon at work in all four categories. (shrink)

Kin selection, reciprocity and group selection are widely regarded as evolutionary mechanisms capable of sustaining altruism among humans andother cooperative species. Our research indicates, however, that these mechanisms are only particular examples of a broader set of evolutionary possibilities.In this paper we present the results of a series of simple replicator simulations, run on variations of the 2–player prisoner's dilemma, designed to illustrate the wide range of scenarios under which altruism proves to be robust under evolutionary pressures. The (...) set of mechanisms we explore is divided into four categories:correlation, group selection, imitation, and punishment. We argue that correlation is the core phenomenon at work in all four categories. (shrink)